Margulis has been right about what is wrong before. She shook up the world of microbiology in 1965 with her outrageous thesis of the symbiotic origin of nucleated cells. To the disbelief of traditionalists, who claimed that free-roaming bacteria cooperated to form cells. Then in 1974, Margulis again rattled the cage of biology by suggesting (jointly with James Lovelock) that atmospheric, geological processes on Earth are so interconnected that they act as a single living, self-regulating system--Gaia. Margulis was now denouncing the modern framework of the century-old theory of Darwinism, which holds that new species build up from an unbroken line of gradual, independent random variations.

Marquis is not alone in challenging the stronghold of Darwinian theory, but few have been so blunt. Disagreeing with Darwin resembles creationism to the uninformed; therefore the stigma that any taint of creationism can bring to a scientific reputation, coupled with the intimidating genius of Darwin, have kept all but the boldest iconoclasts from doubting Darwinian theory in public.

What excites Margulis is the remarkable incompleteness of general Darwinian theory. Darwinism is wrong by what it omits and by what it incorrectly emphasizes.

A number of microbiologists, geneticists, theoretical biologists, mathematicians, and computer scientists are saying there is more to life than Darwinism. They do not reject Darwin's contribution; they simply want to move beyond it. I call them the 'postdarwinians'. Neither Lynn Margulis nor any other postdarwinian denies the true ubiquity of natural selection in evolution. Their disagreement is with the very sweeping nature of the Darwinian argument, the fact that in the end it doesn't explain much, and the emerging evidence that Darwinism alone may not be sufficient to explain all we see. The vital questions the postdarwinians raise are: What are the limits to natural selection? What can’t evolution make? And if blind natural selection has limits, what else is operating within or beyond evolution as we understand it?

According to the ordinary contemporary Darwinian biologist, there is nothing we see in nature that cannot be explained by the elemental process of natural selection. In academic jargon this stance is called selectionism, and the position is nearly universal among biologists working today. Because this stance is more extreme than what Darwin himself believed, it is sometimes neodarwinism.

In the pursuit of artificial evolution, the limits (if any) to natural selection, or to evolution in general, take on practical importance. We'd like an artificial evolution, that generates never-ending diversity, but so far, that isn't so easy to do. We'd like to extend the dynamics of natural selection to very large systems with many levels of scale, but we don't know how far natural selection can be extended. We'd like an artificial evolution that we could control a bit more than we control organic evolution. Is that possible?

Questions like thee have prompted the postdarwinians to reconsider alternative theories of evolution--many that existed before Darwin--that were eclipsed by the dominance of Darwinism. In a kind of intellectual survival of the fittest, contemporary biology places very little importance n these 'inferior' beaten theories, so they survive only in marginal out-of-print books. But the ideas of these creative theories are suited to a new niche called artificial evolution and are cautiously being resurrected for examination.